It’s a compelling notion scientists have long believed: Native Americans have high diabetes rates today because, in ancient times, their ancestors were hunter-gatherers whose genes evolved to help them store fat during famines – biological attributes that have caused problems during modern-day times of plenty.
But new research, based on newly discovered fossilized remnants of ancient Native Americans’ diets, has proven the idea is false. In fact, the University of Nebraska-Lincoln concluded just the opposite is likely to be the case.
The new study, published in the journal Current Anthropology, found prehistoric Native Americans actually consumed high-fiber, low-fat, low-carbohydrate diets that may have altered their genes in ways that leave today’s populations susceptible to disease because of modern-day diets that are high in fat, sugary, high-carb foods that cause rapid spikes in blood glucose.
The idea that "thrifty" genes helped ancient hunter-gatherers store fat for survival was first proposed in the 1960s. But the new study, which is based on an analysis of fossils from an Arizona cave, suggests today’s diabetes diagnoses have more to do with modern-day diet, activity levels and lifestyles than prehistoric factors.
"What we're saying is we don't really need to look to feast or famine as a basis for thrifty genes," said Karl Reinhard, an archaeologist and one the study's authors.
Native Americans have some of the highest rates of type 2 diabetes of any ethnic group, with up to half of adults suffering from the disease in some populations.
The new analysis suggests ancient Native Americans had a diet dominated by maize and high-fiber seeds from sunflowers, wild grasses, pigweed, and amaranth. These were usually ground into flour, cooked and consumed with meat from small mammals, likely rabbit, stewed in water. These foods also have very low glycemic indices, the measure of how fast a food causes blood sugar to increase. High-GI foods may increase the risk of obesity and diabetes.
As a result, researchers suggested, when Native Americans switched to high-fat, high-sugar diets in modern times they were more susceptible to developing diabetes.